1. Field of the Invention
The present invention relates to lifting systems and more particularly to apparatus for lifting pre-cast concrete panels, wherein a part of the lifting apparatus is to be permanently embedded in a cast concrete panel member and is used in conjunction with an engineered lifting hook.
2. Background of the Prior Art
Prestressed, pre-cast concrete panels enjoy great popularity within the building and construction industry. They currently comprise the major component in the construction of many different kinds of structures, such as office buildings, warehouses, schools, parking decks, retention walls, etc. These pre-cast panels are typically fabricated offsite, that is, they are manufactured at a location other than the actual construction site. Most often the offsite manufacturing facility is a factory especially dedicated to producing concrete panels of various types and configurations. Obviously, the large heavy panels manufactured off-site must be loaded on vehicles and then moved to the construction site. Once at the construction site, the panels must be unloaded and placed in their final position relative to the construction.
Referring now to FIG. 1A, depicted is a commonly used prestressed concrete panel member 10 (only a portion of which is depicted) of the type to which the present invention pertains in particular. The concrete panel is manufactured such that during the casting process, an anchor plate of the type depicted in FIG. 1B at 11, is suspended within the concrete matrix in a structurally sound location in order to present cable-lifting holes which will ultimately receive cables for lifting the panel. Such anchor plates are typically positioned throughout a common side of the panel because the weight of even a small concrete panel necessitates that a number of anchoring devices be used to equally distribute the weight, and facilitate safe and precise handling of the finished panels.
Referring to FIGS. 1B through 1D, alternative prior art anchor plates which are similar to plate 11, are depicted at 12 and 13, and are referenced in U.S. Pat. No. 4,627,198 to Francies, which issued in 1986. In FIG. 1E, depicted at 14 is an apparatus for quickly connecting lifting cables to one of the prior art anchor plates and which is capable of repeated use. The various prior art lifting components 11, 12, 13, and 14, shown in FIGS. 1B through 1E, represent the most popular lifting components being utilized today in the lifting and handling of heavy concrete panels. These devices generally provide a secure means of attaching the lifting cables to the concrete panel, while providing a degree of manufacturing convenience and flexibility.
However, when referring again to FIG. 1A, it is seen that the connection recess 17 surrounding the anchor plate 11, makes plate 11 vulnerable to inaccessibility under certain conditions. The foremost problem is blockage of the cable connecting hole that is formed in the anchor plate as a result of water that collects and freezes in the recessed area. During periods of inclement weather, the entire recess, as well as the hole in the anchor plate 11, must either be covered or else it will have to be cleared of frozen material before the lifting cables can be secured within the connection hole. This condition manifests itself as a major inconvenience. Furthermore, the cable connection apparatus 14 that was shown in FIG. 1E is usually used with the anchor plate 11, and that apparatus represents an additional source of potential malfunction and inconvenience due to the device being designed with a rotating spoon-shaped connecting member, as described in U.S. Pat. No. 4,700,979, issued to Courtois et al., in 1987. In the Courtois patent, the cable connecting member is contained within and made a part of a mechanism comprised of a plurality of moving parts, namely a housing, a connecting member, and a retaining pin or shaft. The connecting member rotates or pivots with respect to the shaft, making the design particularly susceptible to wear, inadequate lubrication, rust, abuse, ice, and/or snow.
Although the prior art anchoring plates 11 through 13 have been used without the connecting apparatus 14 of FIG. 1E, or some other analogous quick-connect device, one the greatest downsides of plates 11 through 13, is the numerous manufacturing steps that are required in their fabrication, each step resulting in added costs. Additionally, each design is highly specific to only one particular type of cast panel that it will reside within. In addition, the connection apparatus 14 also requires numerous manufacturing steps.
Thus, all of the above-mentioned prior art anchoring plates, as well as the connection apparatus now being used, suffer from the following disadvantages: the anchor plate connection hole is vulnerable to inaccessibility under inclement weather when freezing occurs; the connection hole usually requires cleaning of frozen material (ice, mud) before the connection apparatus can be secured within the connection hole; the connection apparatus suffers vulnerability to seizing due to ice formation in the mechanism; the anchoring plates require numerous manufacturing steps, specifically notching, punching and drilling steps; the connection apparatus is composed of moving parts which can render the entire unit useless if one of the parts fails; the connection apparatus is particularly susceptible to wear, and is overly complex for the application and expensive to manufacture. Accordingly, it would be desirable to provide a lifting system which would improve upon the technology described above.
One aspect of the invention provides a lifting system which has found particular application for use with pre-cast panels having at least one surface which includes, in a preferred form, a connection recess formed therein, the invention comprising an anchor-lifting device fixed within the connection recess of the pre-cast panel, the anchor-lifting device including at least one connection pin, and a connecting apparatus for engagement with the connection pin to lift the pre-cast panel. The lifting system may also most advantageously include a connection apparatus that is comprised of an engineered lifting hook having a pair of laterally spaced individual hooks, each of which are joined together by a shared coupler and stop plate. The respective hooks also may define an engagement channel which defines a lifting arm. The lifting arm holds the connection pin within the engagement channel during lifting of the pre-cast panel.
The foregoing and other features and advantages of the invention will become further apparent from the following detailed description of the presently preferred embodiments, read in conjunction with the accompanying drawings. The detailed descriptions and drawings are merely illustrative of the invention rather than limiting, the scope of the invention being defined by the appended claims and equivalents thereof.